The present invention relates to a heat conductive resin substrate dissipating heat generated from electronic equipments and a semiconductor package excellent in heat radiation ability.
Recently, a countermeasure of heat generated from the electronic equipment due to advance in integration of the semiconductor package and advance in high integration and speed up of LSI or the like accompanying with advance in performance, miniaturization and weight reduction in the electronic equipment has became to be very important problems.
Conventionally, a method using a printed circuit board made of metal or ceramic with high heat conductivity, a method forming thermal via-holes for dissipating heat in a substrate, a method using metal, ceramic or resin with high heat conductivity as semiconductor-packaging material, or a method interposing grease with high thermal conductivity or a heat conductive rubber with flexibility between a heat-generating source and a radiator or between a heat source and a heat-conducting plate for purpose of reduction in contact thermal resistance or the like have been practiced in order for diffusion of heat by heat-generating element.
Although a known resin substrate, that is, the glass-cloth epoxy resin substrate or the like used in the printed circuit board on which electronic components such as the semiconductor package are equipped is relatively excellent in mechanical property, dimension accuracy, workability of a through-hole and multi-layering as compared with the metal substrate or the ceramic substrate, there is a disadvantage of inferiority in heat conductivity.
Therefore, it has been considered a method filling electrical insulation fillers such as metal oxides, metal nitrides, metal hydroxides and such as an aluminum oxide, a boron nitride, an aluminum nitride, a magnesium oxide, a zinc oxide, a silicon carbide, quartz and an aluminum hydroxide with high thermal conductivity into resin for a resin substrate which high heat conductivity is required.
However, thermal conductivity of the resin substrate into which such heat conductive fillers are filled is to the extent of 3 W/mK at most, therefore, advance in thermal conductivity has been desired earnestly.
According to Japanese Patent Laid-open No.HEI9-255871, a thermoplastic resin composition containing a polybenzasol fiber and the moldings is proposed.
This invention relates to the moldings such as a rigid resin composition, substrate material and case material with impact resistance, toughness, electrical insulation and heat conductivity. However, an upper limit of thermal conductivity of the substrate material obtained by this resin composition is approximately 1 W/mK, whereby heat conductive substrate material and the heat radiation semiconductor package of an object of the invention have not been obtained.
On the one hand, Japanese Patent Laid-open No.HEI11-17369 relates to heat radiation material consisting of a synthetic-resin wire rod with a certain diameter, which organic fibers are blended into a synthetic resin in the longitudinal direction. This heat radiation material is one which the synthetic-resin wire rods consisting of protrusion rods of 5 mm in diameter and 4 mm in length is blended, whereby the heat conductive substrate material and the semiconductor package excellent in heat radiation, of the object of the invention can not be obtained.
Moreover, for the electronic components constituted by a plurality of different materials such as semi-conductive silicon, an alloy of a copper and iron system, aluminum, a solder, a silicon oxide, a nitride, a resin substrate and an adhesive, a countermeasure for malfunctions by a generating thermal stress becomes important because of difference in the thermal expansion coefficients of respective constituting materials. That is, when the thermal expansion coefficient of the resin substrate becomes possible, thermal and electrical reliability is improved, thereby being able to contribute for the industry.
This invention provides a heat conductive substrate which is provided with electrical insulation and high heat conductivity, and is able to control a thermal expansion coefficient, a semiconductor package being excellent in heat radiation ability.
As a result of earnest studying for solving these problems, it has been found that the heat conductive resin substrate which the polybenzasol fibers are arranged in the thick direction and/or in the direction of a surface of the resin substrate, is provided with electrical insulation, and high heat conductivity and the thermal expansion coefficient can be controlled, and this invention is put into practice.
That is, this invention relates to a heat conductive resin substrate wherein the polybenzasol fibers are oriented in the thick direction and/or in the direction of a surface of the resin substrate, and further, a semiconductor package wherein semiconductor chips are mounted on the heat conductive resin substrate which the polybenzasol fibers are oriented in the thick direction and/or in the direction of a surface of the resin substrate.
The polybenzasol fiber used in the heat conductive resin substrate and the semiconductor package according to the invention is a fiber constituted of polybenzasol fiber polymer, and apolybenzasol (PBZ) means polybenzooxasol homopolymer (PBO), polybenzothiasol homopolymer (PBT) and random copolymer, sequential copolymer, block copolymer or graphed copolymer of those PBO and PBT, and is an organic polymer fiber excellent in strength, modulus of elasticity, heat resistance and electrical insulation.
Although a diameter, a shape of the cross section and a length of the polybenzasol fibers are not specified, the length of the fiber is preferable the same length as that of the resin substrate for heat transmission. The reason is that a length is same or the near to the same is the length, the larger becomes the thermal conductivity and a thermal expansion coefficient becomes lower. Moreover, for tensile strength of the polybenzasol fiber, it is preferable 4 G Pa or more and an initial modulus of elasticity for tension is 140 G Pa or more. The heat conductive resin substrate and the semiconductor package according to the invention can show more excellent heat conductivity by arranging in the resin substrate using the polybenzasol fiber which the tensile strength and the initial modulus of elasticity for tension are present within the range thereof.
The heat conductive resin substrate according to the invention comprises a structure that the polybenzasol fibers are oriented in the thick direction and/or in the direction of a surface of the resin substrate. The heat conductivity of the longitudinal direction of the fiber arranged is improved by orienting the polybenzasol fibers in the thick direction and/or in the direction of a surface of the substrate. Moreover, heat conductivity in the any direction which respective polybenzasol fibers are oriented has become possible to increase, as well as the thermal expansion coefficients has become possible to control, by orienting the polybenzasol fibers not only in one direction of the thick direction (hereinafter defined this as a Z direction) or the direction of a surface (hereinafter defined this as a X direction or a Y direction), but also a plurality of directions such as in two directions of the surface, in two directions of the thick direction and one direction within the surface (the Z direction and the X direction), in three directions of the thick direction and two directions within the surface (the Z direction and the X direction and the Y direction), and in three directions or more of the thick direction and two directions or more within the surface (the Z direction and the X direction, the Y direction and an another direction within X Y surface).
The concentration of the polybenzasol fiber allowing to contain in the heat conductive resin substrate is preferably 2 to 80 in volume percent. Improvement in heat conductivity becomes less, and the controlled range of the thermal expansion coefficient also becomes narrow when being less than 2 in volume percent. Workability and easiness of processing become very poor and is not avoided from intrusion of air bubbles when 80 volume percent is exceeded, thereby being not appropriate. The further preferable addition amount of the polybenzasol fiber is 20 to 70 in volume percent, and the yet further preferable addition amount is 40 to 60 in volume percent. Heat conductivity in at least one direction becomes 4 W/mK or more, and this range is preferable.
Moreover, as a fiber except for the polybenzasol fiber, a small quantity of an organic fiber, a natural fiber, a carbon fiber, a metal fiber such as a glass fiber, an alamido fiber, a polyester fiber, a aliphatic polyamide fiber, a vinyl on fiber and a polyethylene fiber, further short fiber and long fiber consisting of composite material which these fibers are compounded, or a small quantity of those woven fabric and non-woven fabric can be mixed.
A kind of resin used in the heat conductive resin substrate according to the invention can not be limited in particular. A thermoplastic resin, thermoplastic elastomer, a thermosetting resin and a cross-linked rubber can be selected in response to the required performance such as hardness, mechanical strength, heat resistance, electrical characteristics, durability and reliability of the heat conductive resin substrate of the object.
As the thermoplastic resin and thermoplastic elastomer, the following can be given: ethylene-xcex1-olefine copolymer such as polyethylene, polypropylene, ethylene-propylene copolymer, a fluoro resin such as polymethyle pentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyvinyl acetal, polyvinylidene fluoride, and polytetrafluoroethylene;
polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyacrylonitrile, styrene-acrylonitrile copolymer, ABS resin, polyphenylene ether and a modified PPE resin, a kind of aliphatic and aromatic polyamide, polyimide, polyamideimide, a kind of polymethacrylic acid ester such as polymethacrylic acid and its methylester;
A thermoplastic resins such as a kind of polyacrylic acid, polycarbonate, polyphenylene sulfide, polysulfone, polyether sulfone, polyether nitrile, polyether ketone, polyketone, liquid crystal polymer, silicone resin, ionomer;
Thermoplastic elastomer such as styrene-butadiene or styrene-isoprene block copolymer and its hydropolymer and styrene system thermoplastic resin elastomer, olefine system thermoplastic elastomer, vinyl chloride system thermoplastic elastomer, polyester system thermoplastic elastomer, polyurethane system thermoplastic elastomer, polyamide system thermoplastic elastomer, or the like.
As the thermosetting resin and the cross-linked rubber, the following can be given: the cross-linked rubber such as an epoxy resin, a polyimide resin, a bismaleimide resin, a benzocyclobutene resin, a phenol resin, an unsaturate polyester resin, a diallyl phthalate resin, a silicone resin, an urethane resin, a thermosetting type polyphenylene ether and modified PPE resin, a natural rubber, a butadiene rubber, an isoprene rubber, a styrene-butadiene copolymerizated rubber, a nitrile rubber, adydronitrile rubber, a chloroprene rubber, an ethylene-propylene rubber, a chlorinated polyethylene, a chlorosulfonated polyethyene, a butyl rubber and a halogenated butyl rubber, a fluororubber, an urethane rubber, a silicone rubber, or the like.
Above all, it is preferable to use at least one kind which is selected from the well-known material; an epoxy resin, a polyimide resin, a bismaleimide resin, a benzocyclobutene resin, a silicone resin, a fluoro resin, a polyphenylene ether resin used as the conventional glass-cloth-mixed resin substrate. For a substance which a dielectric constant and dielectric loss tangent are small and an excellent frequency characteristic in a high-frequency region is required, the fluoro resin, the thermosetting type polyphenylene ether resin, the modified PPE resin, or the polyolefine system resin may be preferably used. Furthermore, used of a polymer alloy consisting of a plurality of resins selected from these resins also is not interfered. Moreover, a cross-link method is not limited to the thermosetting property, but a resin according to the well-known cross-link methods such as a light-setting property and wet-setting properly can be used.
Use in combination with a pre-preg which the conventional glass-cloth base material further is impregnated in the heat conductive resin substrate according to the invention and as other heat conductive filler, use in combination with a metal oxide, a metal nitride, a metal carbide, a metal hydroxide such as a aluminum oxide, a boron nitride, an aluminum nitride, a zinc oxide, a silicon carbide, quartz, an aluminum hydroxide whose thermal conductivity is large and a small quantity of a spherical shape, powdered, fiber-like, needle-like, scale-like or whiskers-like filler consisting of a metal or an alloy such as silver, copper, gold, tin, iron, aluminum, magnesium or carbon, also are not interfered. However, it also is significant feature that the heat conductive resin substrate according to the invention has electrical insulation as far as a conductive additive is not blended, the addition amount should be determine in consideration of the presence or absence of requirements of electrical insulation in usage to be used in the case of blending the conductive filler such as metal and carbon auxiliary subsidiarily.
Since the heat conductive resin substrate according to the invention is excellent in control ability of electrical insulation, high heat conductivity and the thermal expansion coefficient, the substrate can be applied in a radiator, a cooler, a heat sink, a heat spreader, a die pad and a casing or the like which heat radiation ability is required. Moreover, the substrate is applicable for material for the rigid or flexible printed circuit board and material for an insulating substrate of the semiconductor package. In the case of application for the printed circuit board, a subtractive method laminating copper films to process, various additive methods and the well-known method for manufacturing the printed circuit board such as a single layer and one side, a single layer and a double-sided, a multi-layer and a build-up printed circuit boards are applicable.
The semiconductor package according to the invention which semiconductor chips are mounted on the heat conductive resin substrate which the polybenzasol fibers are oriented in the thick direction and/or in the direction of a surface of the resin substrate is effective for the usage requiring heat radiation characteristic which becomes important accompanying with advances in performance, advances in function, advances in high integration, miniaturization and weight reduction. As kinds of the specified structure of the semiconductor package, there are various CSP (a chip-sized package), BGA (a ball-grid array package), QFP (quad flat package) and SOP (a small outline package) or the like, and they are not limited specifically. The substrate can be also utilized as an insulating substrate for MCM (multi-chip module).